From: Alexander Duyck Date: Wed, 14 Dec 2016 15:05:26 -0800 Subject: [PATCH] mm: add support for releasing multiple instances of a page Add a function that allows us to batch free a page that has multiple references outstanding. Specifically this function can be used to drop a page being used in the page frag alloc cache. With this drivers can make use of functionality similar to the page frag alloc cache without having to do any workarounds for the fact that there is no function that frees multiple references. Link: http://lkml.kernel.org/r/20161110113606.76501.70752.stgit@ahduyck-blue-test.jf.intel.com Signed-off-by: Alexander Duyck Cc: "David S. Miller" Cc: "James E.J. Bottomley" Cc: Chris Metcalf Cc: David Howells Cc: Geert Uytterhoeven Cc: Hans-Christian Noren Egtvedt Cc: Helge Deller Cc: James Hogan Cc: Jeff Kirsher Cc: Jonas Bonn Cc: Keguang Zhang Cc: Ley Foon Tan Cc: Mark Salter Cc: Max Filippov Cc: Michael Ellerman Cc: Michal Simek Cc: Ralf Baechle Cc: Rich Felker Cc: Richard Kuo Cc: Russell King Cc: Steven Miao Cc: Tobias Klauser Cc: Vineet Gupta Cc: Yoshinori Sato Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- --- a/include/linux/gfp.h +++ b/include/linux/gfp.h @@ -506,6 +506,8 @@ extern void free_hot_cold_page(struct pa extern void free_hot_cold_page_list(struct list_head *list, bool cold); struct page_frag_cache; +extern void __page_frag_drain(struct page *page, unsigned int order, + unsigned int count); extern void *__alloc_page_frag(struct page_frag_cache *nc, unsigned int fragsz, gfp_t gfp_mask); extern void __free_page_frag(void *addr); --- a/mm/page_alloc.c +++ b/mm/page_alloc.c @@ -3946,6 +3946,20 @@ static struct page *__page_frag_refill(s return page; } +void __page_frag_drain(struct page *page, unsigned int order, + unsigned int count) +{ + VM_BUG_ON_PAGE(page_ref_count(page) == 0, page); + + if (page_ref_sub_and_test(page, count)) { + if (order == 0) + free_hot_cold_page(page, false); + else + __free_pages_ok(page, order); + } +} +EXPORT_SYMBOL(__page_frag_drain); + void *__alloc_page_frag(struct page_frag_cache *nc, unsigned int fragsz, gfp_t gfp_mask) {